A normal eye
The eye brings (parallel) light from distant objects into focus on the back of the eye (the retina) without the internal lens in the eye having to do anything at all.
Axial length percentile graph
Enter values and click Show on graph
Your OD / OS points will appear on the ethnicity- and sex-specific growth chart here.
Why axial length matters
Most childhood myopia is axial — the eye has grown too long. That is why this tracker plots AL, not just the glasses prescription.
Refractive myopia
Refractive myopia is caused by either one or more of the optical surfaces becoming too steep (curvature myopia) and/or where the refractive index of the optical media is too high (index myopia).
Axial myopia
In axial myopia, the optical system is correctly powered but the eyeball has increased in length, increasing the focal length and causing light to be focused in front of the retina.
Sources & methods
- Clinical framing: Poon N. Axial Length: An Essential for Myopia Management. BC Doctors of Optometry.
- European curves: Tideman JWL, et al. Axial length growth and the risk of developing myopia in European children. Acta Ophthalmol. 2018;96(3):301-309. (P25/P50/P75 anchors; intermediate ages interpolated; outer percentiles estimated.)
- East Asian curves: Sanz Diez P, et al. LMS parameters, percentile, and Z-score growth curves for axial length in Chinese schoolchildren in Wuhan. Sci Rep. 2022;12:4850. Ages 6–15 from published LMS tables; 16–18 lightly extended for display.
- Also related: Diez et al. 2019 growth curves; He et al. 2023 Chinese AL/AL-CR percentiles; IMI clinical management guidelines.
- Crystalline lens power: Hernandez VM, et al. Calculation of crystalline lens power using a modification of the Bennett method. Biomed Opt Express. 2015;6(11):4501–4515 (PMC4646557). Based on Bennett AG (1988); thin-lens position and b coefficient per Eqs. 16–18. Remaining buffer is judged with age-adjusted minima (≤ +18.5 D at 6–9 years, ≤ +17.0 D at 10–13, ≤ +15.5 D at 14–18). Use the Bennett buffer calculator.
Using the wrong ethnicity reference can under- or over-estimate risk. Choose the chart that best matches the child's background and discuss with a clinician. This site is provided for educational use in association with Guildford Eye Clinic.
Not a diagnosis. This calculator plots published population percentile charts for education and discussion with an optometrist or ophthalmologist. It does not replace clinical care or optical biometry interpretation.